Results 1 to 15 of 15

Thread: Electrical ground/aluminum boat ?

  1. #1
    Member MRFISH's Avatar
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    1,315

    Default Electrical ground/aluminum boat ?

    I'm fixing up some of the battery wiring on my boat (24' Wooldridge Alaskan II / 200 Merc OB), installing a Blue Seas battery switch and automatic charging relay. Their wiring diagram is pretty straight forward (attached), but it suggests a ground from the negative bus.

    Is that appropriate on an aluminum boat? Wouldn't that give me electrolysis/corrosion issues?

    wiring-blue seas.jpg
    "Fishing relaxes me. It's like yoga, except I still get to kill something." --Ron Swanson

  2. #2
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,246

    Default

    Yes you need a cable going from the negative bus bar to the hull in the transom area. The cable needs to be as large or larger than the negative battery cable/s. You will need a 316 grade S.S. 5/16 or 3/8 bolt, washers and nut at the hull.

    Grounding a aluminum hull to the negative bus bar WILL NOT CAUSE ELECTROLYSIS. In fact if you have a electrolysis problem having a properly grounded hull will reduce the effect of stray current corrosion.

    It best to fix any corrosion problem.

  3. #3
    Member MRFISH's Avatar
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    1,315

    Default

    Quote Originally Posted by MacGyver View Post
    Yes you need a cable going from the negative bus bar to the hull in the transom area. The cable needs to be as large or larger than the negative battery cable/s. You will need a 316 grade S.S. 5/16 or 3/8 bolt, washers and nut at the hull.

    Grounding a aluminum hull to the negative bus bar WILL NOT CAUSE ELECTROLYSIS. In fact if you have a electrolysis problem having a properly grounded hull will reduce the effect of stray current corrosion.

    It best to fix any corrosion problem.
    Thanks for the reply. Could I just attach a non-insulated bus bar to the boat itself? All this is being mounted to the inside of the transom already.
    "Fishing relaxes me. It's like yoga, except I still get to kill something." --Ron Swanson

  4. #4
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,246

    Default

    Never thought about using a non-insulated copper bus bar.

    I can't think of a reason it would not work as long as it can carry several hundred amps and will not corrode over time causing a bad connection.

  5. #5
    Member
    Join Date
    Sep 2014
    Location
    Alaska
    Posts
    354

    Default

    I don't think copper, aluminum, and salt water is a good combination. Maybe I'm missing something here though.

  6. #6

    Default

    "Whoa guys we are getting way confused here over ground and groundING. There is a difference. I will asume for the moment we are talking just dc.

    The ground wire in a DC system is the negative wire, generally black (yelllow in Europe). The red wire is the positive side. Look up the colors codes to find out what color your postive wires should be to different pieces of equipment. http://newboatbuilders.com/pages/elect5.html

    DC systems are two wire systems and although the red is consider the hot side, actually both sides conduct current. It just goes around in a big circle through the red out to the light or whatever, and back to the battery through the black. ABYC standards and ISO and a bunch of other standards, all say the same thing. DON'T USE THE HULL OF A METAL BOAT AS A CONDUCTOR. So you will have a positive wire and a negative wire connected to all your DC electrical equipment.

    The negative side is ground, and this is connected from the battery or from a ground bus (a board with a lot of terminals on it that have a common wire that goes to the negative post on the battery) to the engine block. The engine block is the common ground point.

    So what is a groundING wire? That is the GREEN wire. Yes, DC systems can have a green wire. The green wire is used for two things. One is in case you have a ground fault (an accidental short to ground), the other is for what is commonly called bonding. Bonding is hooking all the metal fittings, metal cases of appliances, etc to the common ground, AND this can include the hull of the boat. ABYC and others allow this because NORMALLY this wire never carries any current.

    Over on the AC side we have a three wire system as well. It also has a green wire (sometimes green with a yellow stripe). That same green wire is connected to the common ground, the engine block and thus to the green wire for the DC system.

    However, as has been rather strongly pointed out the hull is never used as a conductor. This is due to the galvanic corrosion problem, and if you have a AC system with a green wire connected to the common ground, and get a short to ground, now the hull is suddenly conducting 120V ac! And you get AC leakage current into you DC system as well.

    So Do Not use the hull as a ground. It can be connect to the groundING system for protection from galvanic corrosion and stray currents. But not as a conductor."

    This is a quote from BoatDesignNet. If you want to go insane, here is the multi page thread about grounding metal boats:

    http://www.boatdesign.net/forums/onboard-electronics-controls/wiring-aluminum-boat-17557.html



  7. #7
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,246

    Default

    Quote Originally Posted by gbflyer View Post
    I don't think copper, aluminum, and salt water is a good combination. Maybe I'm missing something here though.
    I agree putting copper, aluminum in salt water is a bad idea. When wiring a boat it is with out saying the wiring must be protected from all forms of water.

  8. #8
    Moderator bkmail's Avatar
    Join Date
    Apr 2006
    Location
    Palmer, AK.
    Posts
    4,124

    Default

    Thats why wire ends are tinned, to prevent corrosion to the copper wiring.
    Bk
    BK Marine Services 232-6399
    Planar diesel heaters dealer, service, warranty, and installation.
    Airboats, ocean boats, and river boats serviced.
    https://www.facebook.com/BKMarineServices?fref=ts

  9. #9

    Default

    Quote Originally Posted by bkmail View Post
    Thats why wire ends are tinned, to prevent corrosion to the copper wiring.
    Bk
    Better yet, spring for tinned boat cable, especially for bilge pumps.

  10. #10

    Default

    Quote Originally Posted by gbflyer View Post
    I don't think copper, aluminum, and salt water is a good combination. Maybe I'm missing something here though.
    Definitely not, can cause severe corrosion! There were copper plates from old nav lights on my aluminum cabin, half the aluminum thickness was rotted away under them. Also never use treated wood against aluminum.

    I was always under the impression if you ground back to the negative battery terminal you eliminate most of the stray current and you were not supposed to ground to the hull.

  11. #11

    Default

    While on the subject where tinned was mentioned, here is an interesting bit on what the ABYC (and a guy) has to say about soldered connections. For many, many years I was an advocate of soldered terminals. Guess what:

    http://www.marinewireandcable.com/20...cable-and.html

  12. #12

    Default

    Copperlake, thanks and informative! Still wanna talk new boats at some point. Fishing charters thru the winter and now water taxi duty demanding a new ride at some point!
    What's your thoughts on too many zincs on an aluminum boat?
    Check out Quickwater Adventure water taxi/transport services: https://www.facebook.com/pages/Quick...37553606260978

  13. #13
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,246

    Default

    Quote Originally Posted by copperlake View Post
    "Whoa guys we are getting way confused here over ground and groundING. There is a difference. I will asume for the moment we are talking just dc.

    The ground wire in a DC system is the negative wire, generally black (yelllow in Europe). The red wire is the positive side. Look up the colors codes to find out what color your postive wires should be to different pieces of equipment. http://newboatbuilders.com/pages/elect5.html

    DC systems are two wire systems and although the red is consider the hot side, actually both sides conduct current. It just goes around in a big circle through the red out to the light or whatever, and back to the battery through the black. ABYC standards and ISO and a bunch of other standards, all say the same thing. DON'T USE THE HULL OF A METAL BOAT AS A CONDUCTOR. So you will have a positive wire and a negative wire connected to all your DC electrical equipment.

    The negative side is ground, and this is connected from the battery or from a ground bus (a board with a lot of terminals on it that have a common wire that goes to the negative post on the battery) to the engine block. The engine block is the common ground point.

    So what is a groundING wire? That is the GREEN wire. Yes, DC systems can have a green wire. The green wire is used for two things. One is in case you have a ground fault (an accidental short to ground), the other is for what is commonly called bonding. Bonding is hooking all the metal fittings, metal cases of appliances, etc to the common ground, AND this can include the hull of the boat. ABYC and others allow this because NORMALLY this wire never carries any current.

    Over on the AC side we have a three wire system as well. It also has a green wire (sometimes green with a yellow stripe). That same green wire is connected to the common ground, the engine block and thus to the green wire for the DC system.

    However, as has been rather strongly pointed out the hull is never used as a conductor. This is due to the galvanic corrosion problem, and if you have a AC system with a green wire connected to the common ground, and get a short to ground, now the hull is suddenly conducting 120V ac! And you get AC leakage current into you DC system as well.

    So Do Not use the hull as a ground. It can be connect to the groundING system for protection from galvanic corrosion and stray currents. But not as a conductor."

    This is a quote from BoatDesignNet. If you want to go insane, here is the multi page thread about grounding metal boats:

    http://www.boatdesign.net/forums/onboard-electronics-controls/wiring-aluminum-boat-17557.html


    I'm not confused when it comes to understanding the difference between grounded, grounding and bonding. Blue Sea said to connected the negative bus to a aluminum hull.
    The OP was ask the question “Is that appropriate on an aluminum boat? Wouldn't that give me electrolysis/corrosion issues?”

    I think I answer his question and told him how I would do it with out trying to confuse him.

    If I told him to do what ABYC recommend when grounding a hull to minimize shock hazard to personnel. I would have said to use a 8 gage wire. Instead I said to use heavy cable. The reason I suggested heavy cable has nothing to do with grounding the hull because a 8 gage wire would have been sufficient. It has to do with protecting the boat wiring in the real world.

  14. #14
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,246

    Default

    Quote Originally Posted by BQuad View Post
    Definitely not, can cause severe corrosion! There were copper plates from old nav lights on my aluminum cabin, half the aluminum thickness was rotted away under them. Also never use treated wood against aluminum.

    I was always under the impression if you ground back to the negative battery terminal you eliminate most of the stray current and you were not supposed to ground to the hull.
    That is correct you do not want to use the hull as a negative return (current carrying conductor). The OP was asking about grounding the hull, not the same as ground the hull.

  15. #15
    Member Akgramps's Avatar
    Join Date
    Apr 2008
    Location
    Last civilized place on the planet
    Posts
    2,080

    Default

    Some good info on grounding, bonding etc from David Pascoe

    http://www.yachtsurvey.com/ElectricalSystems.htm

    more here on battery issues
    http://www.yachtsurvey.com/batteries.htm

    Grounds and Grounding
    One of the least understood aspects of a boats electrical system, and the most troublesome, is the proper method of grounding. That we often get questions of whether AC or DC electrical equipment should be grounded to the boat's bonding system is illustrative of this point. AC and DC grounding systems are two separate systems, for distinctly different reasons. If you don't understand these systems, you run the distinct risk of creating a disaster. Actually, there are four separate ground systems: DC ground, AC ground, AC grounding (or bond), and the vessel's bonding system. You can add to this lightning and HF radio grounds as well. Do you know the principles of each? Are you sufficiently confused to discourage you from doing your own wiring? I hope so. For unless you understand each thoroughly, you're headed for trouble.


    The AC ground and grounding systems are "free floating," meaning that they do not ground on the vessel, but only to shore. The ground, or neutral, is a current carrying conductor, and is the source of many troubles because people do not regard it as such. The grounding, bond or green wire is the "safety" intended to channel current safely to ground in the event of a short circuit. Both of these circuits are capable of conducting current and can be the source of electrolysis when there are system faults with the dock or marina wiring. This is very easy to test for.There is only one point where the DC side is grounded, and that is at the battery. It, too, is a "free floating" system in which nothing is ever grounded to any metallic part of the vessel, most especially not the bonding system. Just like a car sitting on rubber tires, completely insulated from earth potential, the battery itself provides the negative potential.The bonding system, also green wire, has nothing to do with electrical systems. Underwater metals are simply wired together to equalize differences in potential of different kinds of metal. Nothing should ever be grounded to the bonding system. Unfortunately, some people don't understand this and use it to ground electrical equipment, occasionally with disastrous results.
    “Nothing worth doing is easy”
    TR

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •